1. Field of the Invention
The field of this invention is a batch control system and process for manufacturing insulation material from two or more ingredients which are blended together in predetermined amounts, according to a specific formula, and extruded to form insulation surrounding a known metallic conductor, such as copper rod.
2. Description of the Prior Art
The monitoring of batching processes for many years has involved the use of a number of different designs employing electronics, timers, controllers, computers, programmable controllers, and other electronic and mechanical devices. Such batching systems convey commodities from one location to another and are commonly used in grain elevator systems, wherein different types of grains from a plurality of bins are conveyed to a common destination to obtain a blend or mixture of commodities. This equipment is often unreliable and confirmation of formula data is extremely difficult to determine visually, through electronics, or through electromechanical parts. Whenever grain blending is performed, discharge gates of the various grain bins are opened based on the percentage of gate opening, not as a percentage of the total flow rate or blend. The percentage of gate opening is frequently different than the percentage of required blend because many extraneous factors affect flow rate. For this reason, the required blending percentages are not accurately derived which leads to a shortcoming of these batching processes.
In more recent times batching systems using minicomputers for the control and monitoring of batching processes have been used successfully, but such batching systems are extremely costly and are only justified for large scale batching operations. When minicomputers have been used as a substitute for prior art relay logic and analog controllers, the cost of the batching system has increased thus not making such batching systems amenable to the use of minicomputers.
Finally, microcomputers have been used to control batching systems. In these systems, to obtain enough speed, often much of the control program had to be written in assembly language. This added greatly to software development and debugging cost, and made field changes to the control program and constants very difficult. Unless a specific debugging device was made available, field debugging of the batching process through the computer was extremely difficult and required a high level of computer skills on the part of a technician.
One example of such a batching system is the Johnson U.S. Pat. No. 3,959,636, incorporated herein by reference thereto, which describes a batching system employing bins, a weighing hopper, a dump and diverter mechanism, a mixer, and a computer control device which includes a basic processor, memory bus structure, and display console. While this computer driven system monitors and controls the batching process, it does not perform the same blending, conveying, control, and interface (with programmable controller) functions as does the computer in the subject invention. More particularly, the Johnson '636 batching system is not suitable for the control and monitoring of a batching system used in the manufacture of insulation for metallic rod because it does not utilize a programmable controller which economically and expeditiously monitors and controls specific steps in the batching process, and provides a debugging means suitable for maintenance technicians unskilled in computer technologies.
Prior to 1984, a batching control system, such as shown in FIG. 1 was used for the manufacture of insulation for metallic rod. Referring to FIG. 1, a formula was entered manually by an operator on a control panel 1. Conveyors 5 forwarded the materials to scales 33 which weighed the material to be made into insulation. The material in the scales was output to valves 4 which directed the materials into 1 of 2 blenders 2. The blenders 2 mixed the various ingredients into a suitable material for futher processing into insulation. The control functions were accomplished by the routing of AC logic signals through various switches and relays to solenoids and motor starter coils. This manual batching system was unreliable, inflexible, and inaccuarate because it was hard-wired and semi-automatic.
Current state of the art is to combine a computer and programmable controller as in the Axelson U.S. Pat. No. 4,527,245. This is done to provide the data handling and display capabilities of a high level language machine, with the control logic, speed, and debugging capability found in current sate of the art programmable controllers. In those state of the art batching systems which utilized a computer and programmable controller in combination, however, such as the Axelson U.S. Pat. No. 4,527,245, the computer and programmable controller were not connected via a network and assumed a master/slave status. The Axelson computer and programmable controller did not monitor and control blenders, scales, valves and conveyor motors through input/output devices, but instead issued commands to a control means (master/slave cylinders) which in turn controlled the opening of a discharge gate means to obtain the required blending percentages.
The subject invention supercedes these state of the art batching systems by incorporating the use of an Allen Bradley Data Highway which is a token passing network designed to remain operational even if one of the attached devices fail. This allows use of modems on the network to establish any fully IBM XT compatible computer as the operator station in case of failure of a TMI computer. It also allows for operation of a debugging terminal concurrent with normal use of the TMI computer and a programmable controller, the PLC 2/30. Operation of this system, moreover, can continue whether or not a computer is available, as long as the programmable controller is reasonably intact.
Another prior art system, depicted in FIG. 2, was used in the period 1984 through 1987 and improved the FIG. 1 pre-1984 batching system. In this system, a programmable controller 6 was used with a series of input/output (I/O) racks 7 to control the blenders 2, valves 4, and conveyor motors 5 and receive inputs from the scales 3, valves 4 and conveyor motors 5 to manufacture insulation for metallic rod. A terminal and operator control panel 8 was used to input desired changes to the system and to deploy desired data. The programmable controllers 6 provided inputs and outputs necessary to control the valves, blowers, screw feeders, etc., which regulated the materials in process and also provided a ladder logic program that optimized real time control of the aforementioned items. The ladder logic program also provided control structures essential to program the driving logic for the system. However, in this 1984-1987 batching system, there was little or no support for mathematical entities over three digits in length, archive data files, data terminal operations, etc., normally associated with the use of a computer. Thus, the traditional programmable controller batching control system was not as accurate as the subject invention and did not have the capability to make the batching system more accurate and reliable.